This invention relates to the art of indwelling sensors for ruminant animals, and more particularly to a new and improved device and method for monitoring selected physiological parameters from within the stomach of ruminant livestock using radio frequency telemetry and external readers and transmitters.
One area of use of the present invention is detecting metabolic diseases in ruminant livestock, although the principles of the invention can be variously applied. Metabolic diseases in ruminant livestock can develop in several forms with different clinical signs and methods of treatment. One of the most common forms is rumen acidosis which may occur in sheep and goats but which has the greatest economic impact when occurring in adult dairy and beef cattle. Symptoms result from the sudden and excessive intake of rapidly fermentable carbohydrates producing a sudden drop in rumen pH below 5.0, and death can occur as rapidly as within 2–5 days.
A second form, subacute rumen acidosis, also known as SARA, has similar origins to the acute form but presents different symptoms and disease progress. SARA is prevalent in both the beef feed lot and the large confinement dairy operations, and it has the greatest economic consequences of all the metabolic disorders. The presence of SARA can be confirmed by invasive methods removing a sample of rumen fluid and immediately testing the pH level. Normal pH levels range from 5.8 to 6t. Serious harmful effects may result over time if affected cows cannot naturally compensate or receive treatment for a pH that declines to and sustains at 5.8 and lower levels such as 5.4. Cattle with SARA complications typically have depressed feed intake and fail to gain weight at the normal rate. SARA affected milking cows show a decline in milk production and have depressed butter fat levels.
When a general examination of a herd suggests the presence of SARA, due to externally visible symptoms, it has been possible to make quantifiable measurement of the rumen pH using one of three methods. In the event the pH is found to be below the desired level, feed formulation changes may be introduced using various buffering agents and other supplements to normalize the rumen pH.
One method, typically employed at research farms, is surgically fitting the cow with a fistula or cannula which is a permanently fixed porthole surgically established in the left topside of the cow giving direct access to the rumen. The opening is equipped with a soft removable plug which allows entry of suction devices to extract rumen samples for pH measurement or placement of an in dwelling pH electrode suspended into the rumen fluid. This procedure is obviously expensive, and while fairly common at research farms is not practical for commercial dairy farms.
Another method utilizes an orally administered flexible tube passed down the esophagus into the reticulum or through the rumen whereby rumen fluid is drawn into the tube which then is removed from the animal for an immediate pH level test. While this method is relatively simple and quick it suffers from the limitations of need to restrain the animal, lack of assurance that the fluid always is drawn from the same location in the rumen each time or from the most important area of the lumen, and the chance that the sample is compromised by saliva containing buffering agents involuntarily released by the animal during the procedure.
The third procedure, heretofore thought to be the most accurate, is known as rumenocentesis wherein a syringe is inserted through the abdominal lower left sidewall of the animal into the rumen cavity for immediate withdrawal of rumen fluid to be pH tested. This has been the recommended method for use on commercial farms and is highly reliable if done properly. However, it is time consuming and expensive due to the need for several people to restrain the animal and the need to surgically prepare the penetration site. Also, there is some risk of infection at the site.
While the foregoing describes metabolic illnesses found in domestic livestock, there are other livestock health problems which call for a device and method for diagnosing and monitoring the animal during a course of treatment.